Justicia americana
American Water Willow
Species Profile
Introduction
To start out this species profile, I'd like to clarify one thing — this is NOT a willow tree. American water willow, despite the similar name, doesn't have bark like a willow tree. With that out for the way, let's get into the weeds!
American water willow, commonly referred to as water willow, grows to various heights depending on site conditions but has been seen up to 5 feet tall in deeper water. It's stem is pale and lime to dark green, with the colors alternating around the stem. Leaves are small and blade-shaped, typically reaching 2-3 inches in length with the similar lime to dark green color as the stem. Stems have multiple distinct nodes, from which leaves, new stem growth and/or roots can grow. Flowers are small, <.5 inch, and white with purple accents. Multiple flowers bloom per plant and multiples will flower from a single stem. This plant is well known for its thick rhizome system, which helps it 'revive' each spring after winter dormancy.
Where does it grow?
Water willow has a naturally-occurring range that stretches from Canada to Texas and from the East Coast to the Midwest. It's common in and around streams, rivers and creeks, but will happily grow in and around ponds and lakes. It most often is found growing in shallow water, 2-4 inches, but can grow in depths of 4-plus feet.
How tough is it?
This is one of the toughest plants we'll discuss. It's known to grow in lakes stocked with grass carp (Ctenopharyngodon idella), a fish known for its ability to consume large amounts of vegetation. Additionally, it can withstand floods and droughts extremely well compared to other aquatic and wetland plants.
How is it beneficial?
The hardy nature of water willow allows it to grow in deeper water than other emergent plants, providing habitat for fish and aquatic bugs. Nodes that have grown roots suspended in the water column, provide excellent habitat for aquatic bugs and freshwater shrimp as well. This habitat indirectly feeds predatory fish and waterfowl via the small fish and aquatic bugs that live around the stems. Seeds and roots on the other hand are sometimes directly consumed by wildlife.
The complex root/rhizome system is also a great tool for erosion control and nutrient abatement. These roots spread vertically and laterally, holding bank and shoreline soils. At the same time, they are taking in nutrients as nutrients flow into the water body they are in or around. This reduces erosion and nutrient inflow in a water system.
How does it spread/grow?
Seeds are generated after flowering in the spring and summer. Division of rhizomes allow for easy manual spreading. Fragmentation of stems is likely the easiest way to spread this plant to new areas. A cutting with 3-plus nodes can be successfully planted simply by sticking it in moist soils or shallow water.
How to discern it from other plants?
As mentioned earlier, water willow doesn't have bark. This is the easiest way to distinguish it from a willow tree. Willow tree saplings can look similar but often have maroon to red coloring along the stem. American water willow only has shades of green.
Smaller 'juvenile' smart weeds can be confused with water willow because their leaf shape is similar and nodes are present along the stems. The smartweed, like the willow tree saplings, will have red coloring on its stem. Water willow will only have shades of green. The nodes of smartweed are also much larger, compared to stem diameter, than that of water willow nodes.
What else should you know about this plant?
Water willow is not ideal for every pond. If you're looking to have a manicured lawn all the way to the water, this isn't the plant for you. Water willow grows taller than the grass, leaving you to remove it in some way to maintain the manicured look.
It can spread easily and isn't recommended for small ponds, <.5-1 acre. Although not detrimental, the spread of water willow in a small pond could lead to issues associated with aquatic weed overgrowth, such as limited bank fishing access.
Water willow, in lentic systems (lakes and ponds) typically grows in circular stands. Different diameter and stem densities (number of stems/sqft.) of stands will have variable types, sizes and numbers of fish and/or aquatic bugs. For example, a 3 feet diameter stand with 3 stems/sqft will likely have fewer species and fewer individual aquatic bugs and fish than a 6 feet diameter stand with 10 stems/sqft.
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